Gretchen Reynolds
If you’re a serious runner, tennis player, bushwalker, skier or even ballet dancer, you’ve probably heard from well-meaning strangers that you’re going to ruin your knee or hip joint because of all the pounding with each stride, slice, step, schuss or plie.
But a large-scale new study found that people with hip arthritis who participated in high-impact activities such as jogging and tennis were about half as likely to later have a hip replacement as those who didn’t do high-impact pursuits.
They also didn’t increase their risks for a knee replacement.
The study, published this month in the British Journal of Sports Medicine, involved almost 18,000 men and women with either hip or knee arthritis, most in their 60s.
The results indicate that if people have arthritis, “there isn’t a need to stop or avoid” high-impact activities such as running out of concern the exercise inevitably will exacerbate joint problems, says Bernard Liew, a senior lecturer in biomechanics at the University of Essex in England and lead author of the new study.
The study even raises the intriguing possibility that forceful exercise might be beneficial for some affected joints.
High-impact exercise may strengthen joints
As a longtime runner, I’m used to being warned my knees and hips are doomed. The idea that high-impact activities will inevitably harm joints is widespread.
It’s also understandable. Movements that involve jumping, twisting and hard landings send hefty forces barrelling through the knees and hips. Why wouldn’t those forces damage or wear away any intervening cartilage, tendons or bones?
But a number of past studies have shown the reverse: that running and similar high-impact exercise rarely lead to arthritis in healthy people. There’s even evidence that such activity may strengthen the joints’ cartilage and bones.
Most of those studies looked at healthy joints, primarily knees, and whether they developed arthritis after high-impact exercise, not arthritic joints and whether they worsened.
That distinction matters, because vigorous exercise, especially running, is known to reduce risks for cardiovascular disease, cancer, Type 2 diabetes and many other conditions, as well as premature death. If people with arthritis are told to avoid running and similar exercise, they might miss out on some or all of those benefits.
Does running make arthritic joints worse?
This prompted Liew and his colleagues to focus the new study on people with existing knee or hip arthritis and what happens if they regularly jog or otherwise exercise with high impacts.
The scientists turned to one of the world’s largest databases of arthritis-related data, known as the Good Life with Osteoarthritis in Denmark study. The study includes health and lifestyle information about tens of thousands of Europeans with arthritis. Most of them completed detailed questionnaires about their exercise and other habits when they joined the study.
The researchers drew records for 11,750 men and women with knee arthritis and another 5911 men and women with hip arthritis.
Using their answers about exercise, the scientists categorised people’s workouts as low intensity, meaning brief, easy strolls or no exercise at all; moderate intensity, which mostly meant brisk walking; high intensity, which included cycling, swimming and other strenuous but low-impact exercise; and high impact.
The researchers defined high-impact exercise as those involving contact with the ground, causing forces to run up and down the legs. Running was the most-common high-impact exercise, followed by activities like singles tennis, skiing, soccer, gymnastics, ballet and heavy backpacking. Basketball, volleyball, other forms of dance and jump rope also would qualify.
The researchers then checked into whether people underwent a knee or hip replacement within a year of joining the Danish arthritis database, suggesting their condition had grown worse in the interim.
Fewer hip replacements with high-impact exercise
About six per cent of the men and women with hip or knee arthritis were high-impact exercisers, the researchers found.
Those with hip arthritis who completed that kind of exercise proved to be far less likely to have had a hip replacement within the study period, even when the researchers controlled for age, sex and other common factors.
Their hips were replaced at about half the rate of people with hip arthritis in any of the other groups, including those who did high-intensity but low-impact exercise like cycling or swimming.
The results for knee replacements were more muted but still encouraging. People with knee arthritis completing high-impact exercise were no more likely to get knee replacements than anyone else.
The exercise, in other words, didn’t seem to be making their knees worse.
Try the exercises that work best for you
“From an evolutionary perspective, these findings make sense,” says David Raichlen, a professor of biological sciences and anthropology at the University of Southern California in Los Angeles. He studies human movement, health and evolution, but wasn’t involved with the new study.
“Humans evolved to walk and run long distances throughout life,” Raichlen says. “Our joints evolved expecting regular mechanical loading, not prolonged inactivity. That doesn’t mean everyone with arthritis should start running, but it does suggest that the old idea that impact inevitably destroys joints is probably too simplistic.”
The study has limitations, primarily that it’s not a randomised trial, with people assigned at random to different exercise routines. “While studies like this can provide valuable insights, their findings must be interpreted carefully,” says Grace Hsiao-Wei Lo, an associate professor of immunology, allergy and rheumatology at Baylor College of Medicine in Houston. She’s studied running and knee arthritis but wasn’t part of the new study.
The runners or those doing similar high-impact exercise in this study might also be people with relatively minor arthritis and little joint pain, she says, meaning they’d naturally be less likely to get joint replacements than people who don’t run because it hurts.
The researchers did assess people’s reported joint pain levels, Liew says, and didn’t find relationships between their pain, activity levels and joint replacements. But they can’t rule out that those who ran or did similar exercise were somehow unique.
The study also doesn’t tell us how high-impact exercise might be affecting joints. Exercise like running has been associated with lower inflammation throughout the body and inflammation is believed to be a primary cause of knee arthritis, Liew says. At the same time, forces moving through the joints, especially the hips, with each impact might be prompting the joints’ cartilage and bones to respond and adapt in healthy ways.
Finally, the study didn’t look into how much or little high-impact exercise could be enough or too much for joint health. But Liew suggests thinking small. “When people think of running, they often go to the extreme of a marathon,” he says. But one or two minutes of jogging could be a good start. “Just take a lap around your neighbourhood,” he says.
Talk with your doctor if you have arthritis and are considering starting or continuing running or similar exercise. If the exercise hurts or simply isn’t fun, stop. You don’t have to run – or play tennis, ski or otherwise engage in high-impact workouts – if you don’t want to.
Look for whatever form of movement works for you, Liew says. For his part, he’s developed signs of early hip arthritis, he says, and was sidelined recently by a minor hip procedure. But as soon as he could, he returned to light jogging.
Washington Post
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